DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Header

Mercurial (35bba5f95485)

VCS Links

Line Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "mozilla/ScopeExit.h"
#include "mozilla/StaticPrefs_page_load.h"
#include "mozilla/Unused.h"
#include "mozilla/ipc/IdleSchedulerParent.h"
#include "nsIPropertyBag2.h"
#include "nsSystemInfo.h"
#include "nsThreadUtils.h"
#include "nsITimer.h"

namespace mozilla {
namespace ipc {

base::SharedMemory* IdleSchedulerParent::sActiveChildCounter = nullptr;
std::bitset<NS_IDLE_SCHEDULER_COUNTER_ARRAY_LENGHT>
    IdleSchedulerParent::sInUseChildCounters;
LinkedList<IdleSchedulerParent> IdleSchedulerParent::sDefault;
LinkedList<IdleSchedulerParent> IdleSchedulerParent::sWaitingForIdle;
LinkedList<IdleSchedulerParent> IdleSchedulerParent::sIdle;
AutoTArray<IdleSchedulerParent*, 8>* IdleSchedulerParent::sPrioritized =
    nullptr;
Atomic<int32_t> IdleSchedulerParent::sCPUsForChildProcesses(-1);
uint32_t IdleSchedulerParent::sChildProcessesRunningPrioritizedOperation = 0;
nsITimer* IdleSchedulerParent::sStarvationPreventer = nullptr;

IdleSchedulerParent::IdleSchedulerParent() {
  sDefault.insertBack(this);

  if (sCPUsForChildProcesses == -1) {
    // nsISystemInfo can be initialized only on the main thread.
    // While waiting for the real logical core count behave as if there was just
    // one core.
    sCPUsForChildProcesses = 1;
    nsCOMPtr<nsIThread> thread = do_GetCurrentThread();
    nsCOMPtr<nsIRunnable> runnable =
        NS_NewRunnableFunction("cpucount getter", [thread]() {
          // Always pretend that there is at least one core for child processes.
          // If there are multiple logical cores, reserve one for the parent
          // process and for the non-main threads.
          nsCOMPtr<nsIPropertyBag2> infoService =
              do_GetService(NS_SYSTEMINFO_CONTRACTID);
          if (infoService) {
            int32_t cpus;
            nsresult rv = infoService->GetPropertyAsInt32(
                NS_LITERAL_STRING("cpucount"), &cpus);
            if (NS_SUCCEEDED(rv) && cpus > 1) {
              sCPUsForChildProcesses = cpus - 1;
            }

            // We have a new cpu count, reschedule idle scheduler.
            nsCOMPtr<nsIRunnable> runnable =
                NS_NewRunnableFunction("IdleSchedulerParent::Schedule", []() {
                  if (sActiveChildCounter && sActiveChildCounter->memory()) {
                    static_cast<Atomic<int32_t>*>(sActiveChildCounter->memory())
                        [NS_IDLE_SCHEDULER_INDEX_OF_CPU_COUNTER] =
                            static_cast<int32_t>(sCPUsForChildProcesses);
                  }
                  IdleSchedulerParent::Schedule(nullptr);
                });
            thread->Dispatch(runnable, NS_DISPATCH_NORMAL);
          }
        });
    NS_DispatchToMainThread(runnable);
  }
}

IdleSchedulerParent::~IdleSchedulerParent() {
  // We can't know if an active process just crashed, so we just always expect
  // that is the case.
  if (mChildId) {
    sInUseChildCounters[mChildId] = false;
    if (sActiveChildCounter && sActiveChildCounter->memory() &&
        static_cast<Atomic<int32_t>*>(
            sActiveChildCounter->memory())[mChildId]) {
      --static_cast<Atomic<int32_t>*>(
          sActiveChildCounter
              ->memory())[NS_IDLE_SCHEDULER_INDEX_OF_ACTIVITY_COUNTER];
      static_cast<Atomic<int32_t>*>(sActiveChildCounter->memory())[mChildId] =
          0;
    }
  }

  if (mRunningPrioritizedOperation) {
    --sChildProcessesRunningPrioritizedOperation;
  }

  if (isInList()) {
    remove();
    if (sDefault.isEmpty() && sWaitingForIdle.isEmpty() && sIdle.isEmpty()) {
      delete sActiveChildCounter;
      sActiveChildCounter = nullptr;

      if (sStarvationPreventer) {
        sStarvationPreventer->Cancel();
        NS_RELEASE(sStarvationPreventer);
      }
    }
  }

  Schedule(nullptr);
}

IPCResult IdleSchedulerParent::RecvInitForIdleUse(
    InitForIdleUseResolver&& aResolve) {
  // Create a shared memory object which is shared across all the relevant
  // processes. Only first 4 bytes of the allocated are used currently to
  // count activity state of child processes
  if (!sActiveChildCounter) {
    sActiveChildCounter = new base::SharedMemory();
    size_t shmemSize = NS_IDLE_SCHEDULER_COUNTER_ARRAY_LENGHT * sizeof(int32_t);
    if (sActiveChildCounter->Create(shmemSize) &&
        sActiveChildCounter->Map(shmemSize)) {
      memset(sActiveChildCounter->memory(), 0, shmemSize);
      sInUseChildCounters[NS_IDLE_SCHEDULER_INDEX_OF_ACTIVITY_COUNTER] = true;
      sInUseChildCounters[NS_IDLE_SCHEDULER_INDEX_OF_CPU_COUNTER] = true;
      static_cast<Atomic<int32_t>*>(
          sActiveChildCounter
              ->memory())[NS_IDLE_SCHEDULER_INDEX_OF_CPU_COUNTER] =
          static_cast<int32_t>(sCPUsForChildProcesses);
    } else {
      delete sActiveChildCounter;
      sActiveChildCounter = nullptr;
    }
  }
  Maybe<SharedMemoryHandle> activeCounter;
  SharedMemoryHandle handle;
  if (sActiveChildCounter &&
      sActiveChildCounter->ShareToProcess(OtherPid(), &handle)) {
    activeCounter.emplace(handle);
  }

  uint32_t unusedId = 0;
  for (uint32_t i = 0; i < NS_IDLE_SCHEDULER_COUNTER_ARRAY_LENGHT; ++i) {
    if (!sInUseChildCounters[i]) {
      sInUseChildCounters[i] = true;
      unusedId = i;
      break;
    }
  }

  // If there wasn't an empty item, we'll fallback to 0.
  mChildId = unusedId;

  aResolve(Tuple<const mozilla::Maybe<SharedMemoryHandle>&, const uint32_t&>(
      activeCounter, mChildId));
  return IPC_OK();
}

IPCResult IdleSchedulerParent::RecvRequestIdleTime(uint64_t aId,
                                                   TimeDuration aBudget) {
  mCurrentRequestId = aId;
  mRequestedIdleBudget = aBudget;

  remove();
  sWaitingForIdle.insertBack(this);

  Schedule(this);
  return IPC_OK();
}

IPCResult IdleSchedulerParent::RecvIdleTimeUsed(uint64_t aId) {
  if (mCurrentRequestId == aId) {
    // Ensure the object is back in the default queue.
    remove();
    sDefault.insertBack(this);
  }
  Schedule(nullptr);
  return IPC_OK();
}

IPCResult IdleSchedulerParent::RecvSchedule() {
  Schedule(nullptr);
  return IPC_OK();
}

IPCResult IdleSchedulerParent::RecvRunningPrioritizedOperation() {
  ++mRunningPrioritizedOperation;
  if (mRunningPrioritizedOperation == 1) {
    ++sChildProcessesRunningPrioritizedOperation;
  }
  return IPC_OK();
}

IPCResult IdleSchedulerParent::RecvPrioritizedOperationDone() {
  MOZ_ASSERT(mRunningPrioritizedOperation);

  --mRunningPrioritizedOperation;
  if (mRunningPrioritizedOperation == 0) {
    --sChildProcessesRunningPrioritizedOperation;
    Schedule(nullptr);
  }
  return IPC_OK();
}

int32_t IdleSchedulerParent::ActiveCount() {
  if (sActiveChildCounter) {
    return (static_cast<Atomic<int32_t>*>(
        sActiveChildCounter
            ->memory())[NS_IDLE_SCHEDULER_INDEX_OF_ACTIVITY_COUNTER]);
  }
  return 0;
}

void IdleSchedulerParent::Schedule(IdleSchedulerParent* aRequester) {
  if (sWaitingForIdle.isEmpty()) {
    return;
  }

  if (!aRequester || !aRequester->mRunningPrioritizedOperation) {
    int32_t activeCount = ActiveCount();
    // Don't bail out so easily if we're running with very few cores.
    if (sCPUsForChildProcesses > 1 && sCPUsForChildProcesses <= activeCount) {
      // Too many processes are running, bail out.
      EnsureStarvationTimer();
      return;
    }

    if (sChildProcessesRunningPrioritizedOperation > 0 &&
        sCPUsForChildProcesses / 2 <= activeCount) {
      // We're running a prioritized operation and don't have too many spare
      // cores for idle tasks, bail out.
      EnsureStarvationTimer();
      return;
    }
  }

  // We can run run an idle task. If the requester is prioritized, just let it
  // run itself.
  RefPtr<IdleSchedulerParent> idleRequester;
  if (aRequester && aRequester->mRunningPrioritizedOperation) {
    aRequester->remove();
    idleRequester = aRequester;
  } else {
    idleRequester = sWaitingForIdle.popFirst();
  }

  sIdle.insertBack(idleRequester);
  Unused << idleRequester->SendIdleTime(idleRequester->mCurrentRequestId,
                                        idleRequester->mRequestedIdleBudget);
}

void IdleSchedulerParent::EnsureStarvationTimer() {
  // Even though idle runnables aren't really guaranteed to get run ever (which
  // is why most of them have the timer fallback), try to not let any child
  // process' idle handling to starve forever in case other processes are busy
  if (!sStarvationPreventer) {
    // Reuse StaticPrefs::page_load_deprioritization_period(), since that
    // is used on child side when deciding the minimum idle period.
    NS_NewTimerWithFuncCallback(
        &sStarvationPreventer, StarvationCallback, nullptr,
        StaticPrefs::page_load_deprioritization_period(),
        nsITimer::TYPE_ONE_SHOT_LOW_PRIORITY, "StarvationCallback");
  }
}

void IdleSchedulerParent::StarvationCallback(nsITimer* aTimer, void* aData) {
  if (!sWaitingForIdle.isEmpty()) {
    RefPtr<IdleSchedulerParent> first = sWaitingForIdle.getFirst();
    // Treat the first process waiting for idle time as running prioritized
    // operation so that it gets run.
    ++first->mRunningPrioritizedOperation;
    ++sChildProcessesRunningPrioritizedOperation;
    Schedule(first);
    --first->mRunningPrioritizedOperation;
    --sChildProcessesRunningPrioritizedOperation;
  }
  NS_RELEASE(sStarvationPreventer);
}

}  // namespace ipc
}  // namespace mozilla